A feature was added in ZDoom wherein UDMF format allows you to use multiple tags per sector. This is an extremely useful feature, and one that is now being used by mappacks that thus cannot be played online even though they have multiplayer compatibility.

Fast-tracking support for this would allow more modern mapsets to be played on Zandro instead of just Boom and old ZDoom stuff. This is potentially good for activity since survival is the most popular gamemode.

I'm working on a multiplayer megawad with Tron styled maps in UDMF format. The option to use multiple tags for more 3D sectors would allow me to improve the design of these maps. 3D sectors are very helpful to bring legit Tron feeling into DooM maps.